[libcamera-devel] softISP for libcamera

[Laurent Pinchart]

On Wed, Dec 06, 2023 at 03:13:32PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > Thanks a lot, I got this all to work on pinephone.
> > > 
> > > I'd really like to see statistics gathering separated from
> > > debayer.
> > > 
> > > Another thing is that soft IPA is a bit too simplistic
> > > (soft_linaro.cpp):
> > > 
> > >         /*
> > >          * Try to use the minimal possible analogue gain.
> > >          * The exposure can be any value from exposure_min_ to exposure_max_,
> > >          * and normally this should keep the frame rate intact.
> > >          */
> > > 
> > > That will result in shooting at 1/15, ISO50 -- resulting in blurry
> > > photos (motion) -- even with sensors that could shoot at ISO500
> > > without getting grainy. RPI pipeline has support for this, with config
> > > file saying "stay at ISO50 to 1/60, then move iso up to ISO200 @ 1/60,
> > > then start adjusting exposure again". It would be nice to reuse it.
> > 
> > Let's please not refer to "ISO" in technical discussions. The ISO 12232
> > standard is pretty much useless, "ISO" values are only meant for
> > marketing.
> 
> Well, I believe "marketing ISO" is good enough to demonstrate my point
> here :-). It is familiar "unit" to people doing photography. What
> would you suggest as replacement?

Just analog gain. There's nothing anywhere that maps a x1.0 analog gain
to ISO 50, 100, 200 or any other value.

> Anyway "minimal possible gain" is too simple solution for many cases.

That I don't dispute :-)

Also note that there's no reason for going lower than x1.0, even if the
sensor supports lower values.

-- 
Regards,

Laurent Pinchart